PHP 5 Sessions

A session is a way to store information (in variables) to be used across multiple pages.

Unlike a cookie, the information is not stored on the users computer.

What is a PHP Session?

When you work with an application, you open it, do some changes, and
then you close it. This is much like a Session. The computer knows who you are.
It knows when you start the application and when you end. But on the internet
there is one problem: the web server does not know who you are or what you do,
because the HTTP address doesn't maintain state.

Session variables solve this problem by storing user information
to be used across multiple pages (e.g. username, favorite color, etc). By
default, session variables last until the user closes the browser.

So; Session variables hold information about one single user, and are available to all pages in one application.

Tip: If you need a permanent storage, you may want to store the data in a
database.

Start a PHP Session

A session is started with the session_start() function.

Session variables are set with the PHP global variable: $_SESSION.

Now, let's create a new page called "demo_session1.php". In this page, we start a
new PHP session and set some session variables:

Example

Most sessions set a user-key on
the user's computer that
looks something like this: 765487cf34ert8dede5a562e4f3a7e12. Then, when a
session is opened on another page, it scans the computer for a user-key. If
there is a match, it accesses that session, if not, it starts a new session.

Modify a PHP Session Variable

To change a session variable, just overwrite it:

Example

<?phpsession_start();?><!DOCTYPE html><html><body>

<?php// to change a session variable, just overwrite it $_SESSION["favcolor"] = "yellow";print_r($_SESSION);?>

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